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Caption

Magnolia leaf decomposing. Coloured image of a leaf of Magnolia grandiflora in the process of decomposition. The skeleton of leaf veins (green lines) is seen. Other green and yellow areas on the leaf edge and between the veins show the breakdown of leaf tissues (mesophyll). Leaves rot away due to the action of micro-organisms in the soil, notably bacteria and fungi. Mesophyll decomposes first, leaving a network of veins which in life conducted water through the leaf. The veins are made up of cellulose and lignin, substances more resistant to decomposition. Eventually the leaf skeleton of veins breaks up mechanically to form part of the soil humus.